1. Field of the Invention
The present invention generally relates to a patient interface device for use in a pressure support system that supplies a flow of gas to the airway of a patient, and, in particular to a patient interface device that includes a forehead and a chin support system and to a pressure support system that includes such a patient interface device.
2. Description of the Related Art
There are numerous situations where it is necessary or desirable to deliver a flow of breathing gas non-invasively to the airway of a patient, i.e., without intubating the patient or surgically inserting a tracheal tube in their esophagus. For example, it is known to ventilate a patient using a technique known as non-invasive ventilation. It is also known to deliver continuous positive airway pressure (CPAP) or variable airway pressure, such as a bi-level pressure that varies with the patient's respiratory cycle or an auto-titrating pressure that varies with the monitored condition of the patient. Typical pressure support therapies are provided to treat a medical disorder, such as sleep apnea syndrome, in particular, obstructive sleep apnea (OSA), or congestive heart failure.
Non-invasive ventilation and pressure support therapies involve the placement of a patient interface device, which is typically a nasal or nasal/oral mask, on the face of a patient to interface the ventilator or pressure support system with the airway of the patient so that a flow of breathing gas can be delivered from the pressure/flow generating device to the airway of the patient. It is known to maintain such masks on the face of a patient by a headgear having upper and lower straps, each having opposite ends threaded through connecting elements provided on the opposite sides and top of a mask.
Because such masks are typically worn for an extended period of time, a variety of concerns must be taken into consideration. For example, in providing CPAP to treat OSA, the patient normally wears the patient interface device all night long while he or she sleeps. One concern in such a situation is that the patient interface device is as comfortable as possible, otherwise the patient may avoid wearing the interface device, defeating the purpose of the prescribed pressure support therapy. It is also important that the interface device provide a tight enough seal against a patient's face without discomfort. A problem arises in that in order for the mask to maintain a seal without any undue gas leaks around the periphery of the mask, the mask may be compressed against the patient's face. This is most notable, for example, in masks having a bubble type cushion. While the bubble cushion itself is comfortable, it does not provide adequate support which may cause gas leaks around the periphery of the mask. The bubble effect is diminished when the headgear strap force is increased to improve stability.
It is known to provide a patient interface device that includes a forehead support that contacts the patient's forehead to provide a support mechanism between the mask and the patient's forehead. Gas delivery masks having forehead cushions, spacers or supports are described, for example, in U.S. Pat. Nos. 4,907,584; 5,243,971; 5,517,986; 5,570,689; 6,119,693; and 6,357,441; 6,467,483. The forehead supports prevent the mask from exerting too much force on a patient's face and provides stability to the mask.
Another mask with forehead support is disclosed in International Publication No. WO 00/78384 A1. In this arrangement a forehead support is adapted to be secured to a respiratory mask. The forehead support includes a joining member for securing to the mask and a cushion frame pivotally mounted to the joining member.
However, an advantage exists for increased stability of the gas delivery mask support. Another advantage exists for a support which evenly distributes headgear strapping force by utilizing both forehead and chin supports. A further advantage exists for increased isolation of the gas delivery mask support from the mask cushion.